I've brought this up before, but I'd recommend pirouetting circuits. Nothing that has been suggested so far are true "3D" moves by the definition most people go by. I've been practicing them a lot on the sim for the past month and I'm still having trouble being consistent with it. Although it's a difficult move to nail down, I think it's great for taking your orientation skills to the next level, as your constantly changing cyclic to keep the circuit.

In my opinion it's one of the most graceful moves there is. A perfectly level, constant radius constant piro inverted pirouetting funnel (that's a mouthful) is one of those moves that makes you think, "How can that be?" You don't see a whole lot of people doing it and it's a change from the usual stick banging, pitch pumping style of flying most people do.